ISSN print edition: 0366-6352
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Synthesis and characterization of a novel Schiff base and its enhancement on flame retardancy of epoxy resins

Ge-Yun You, Hong-Wu He, Bin Feng, Yu-Ying Tang, Fang-Fang Fan, Zhi-Quan Cheng, Chang-Jie Yang, and Cong Liang

College of Chemistry and Environmental Engineering, Baise University, Baise, People’s Republic of China



Received: 25 July 2019  Accepted: 13 January 2020


A novel Schiff base, namely N1,N2-bis{3,4-bis(5,5-dimethyl-2-oxide-1,3,2-dioxaphosphinan-2-yl)oxy]benzylidene}ethane-1,2-diamine (PN), was synthesized by the condensation of 3,4-bis[(5,5-dimethyl-2-oxido-1,3,2-dioxaphosphinan-2-yl)oxy] benzaldehyde (PCHO) and ethylenediamine. Its chemical structure was characterized by 1H, 13C, 31P NMR, mass spectra and elemental analysis. PN was used as an additive flame retardant to improve the flame retardancy of diglycidyl ether of bisphenol A (DGEBA) cured by 4,4′-diaminodiphenylsulfone (DDS) with different phosphorus mass fraction. The incorporation of PN promoted DGEBA/DDS to yield more char residues under both nitrogen and air atmosphere, and exhibit good flame retardancy. With 1.5 wt% phosphorus mass fraction, PN-1.5/DGEBA/DDS could reach the highest flame retardant level of V-0 rating for UL-94 vertical burning test, obtain a limiting oxygen index (LOI) value of 32.4%, and keep relatively good mechanical properties by 81.52% of flexural strength and 90.40% of Izod impact strength compared with DGEBA/DDS. The flame-retardant mechanism researches revealed that PN presented a comprehensive mechanism of condensed phase, gas phase and phosphorus-nitrogen synergistic effect in DGEBA/DDS system.

Keywords: Epoxy resin; Phosphorus-nitrogen; Flame retardancy; Mechanical performance; Flame-retardant mechanism

Full paper is available at

DOI: 10.1007/s11696-020-01067-8


Chemical Papers 74 (7) 2201–2210 (2020)

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